Coal pulverizer



L'MZ 79 2 Sheets-Sheet l June 1U, W30. H. H. BATES COAL PULVERIZER FiledApril 25, 1927 ATTORNEY H. H. BATES COAL PULVERIZER June IU, 1930.

Filed April 25, 1927 2 Sheets-Sheet' 2 CL im ATTORNEY WITNESS l PatentedJuneV 10, 1930 UNITED STATES PATENT f OFFICE HARRY H. BATES, or RIDLEYPARK, rnNNsYLvANIA'A'ssIGNOR To wEsTINGHOUsE ELECTRIC a MANUFACTURINGCOMPANY, A CORPORATION OF PENNSYLVANIA oo AL rUIyRRIznR Application medApril 25, 1927. Serial No. 186,457.

My invention relates to grinding machines, for example, machines forgrinding coal into pulverous form for use in furnaces, and has for itsobject to provide apparatus of .the

character designated which shall be relatively small and compact andwhich shall have a Apparatus embodying features of my in- Y ventionisillustrated in the-accompanying 20 drawings, in which:

Fig. 1 is a longitudinalsection view of apparatus embodying features ofmy inven-V tion' V Fig. 2 is a sectional view'taken along the line II-IIof Fig. 1 and looking in the direction of the arrows;

Fig. 3 is a perspective view ofthe station-v ary grinding stone employedin my invention;

Fig. 4 is a view, in elevation, showing a modified form of rotatinggrinding stone; Fig. 5 is a sectional view similar to Fig. 1 but showinga grinding machine embodying a plurality of grinding units; Y

Fig. 6 is a view similar to Fig. 1 and showing a further modified formof my invention; and, Fig. 7 is a fragmentary. sectional view takenalong the line VII-VII of Fig. 4.

I-Ieretofore, in the design of grinding machines for` pulverized fuel,among the difculties to be overcome there has been that of producing amachine which is effective to reduce the fuel to a sufficiently finelydivided state in one passage through the machine that it might beemployed in a pulverized fuel burning furnace and also in providing amachine which hasa relatively high output for the Apower required todrive it. 50 I have discovered that these and other 'element andavcoaxially arrange diiculties may be overcome by providing a machineembodying a stationary indmg rotary grinding element cooperating withthe stationary element and in arranging the grinding elements withconjugate working faces. I provide, in the working face of the station#ary element, a feed groove whichforms one of the important features ofmy invention, and which extends from the periphery in a chordaldirection, to one side of the axis of the stone and is so disposed thatthe action of the working face of therotary element in passing thegroove exerts an inward force on the material in the groove therebyproducing apacking and crushing action on said material before Vitactually passes between the working faces of the two stones. The

Vfeeding groove is generally wedge-shaped and uniformly decreases indepth from the peripheryinwardly of the stone. Inorder to providesuicient length to the groove, it may be turned arcuately around theaxis of the stationary. element as it approaches inwardly of saidelement.

In order to avoid overheating of the stones in service,'I provide themwith hollow retaining members which embrace the stones and provide meansfor circulating a cooling fluid through the retaining members on theAside opposite the working faces thereof. The stationary member isyieldingly held in a predetermined working relation with respect to therotary member, and should some foreign material, such as iron or otherhard material which would endanger the stones, accidentally pass intothe machine, the yielding means permit a separation of the stones andthus prevent danger to the machine. I may also provide means effectiveupon such 90 relative displacement of the stones to shut oii' the supplyof material to be ground to the' machine and thus prevent an undueamount of coarse -material from passing through the machine.

Referring now to the drawings for a better understanding of myinvention, I show, in Fig. 1, my improved grinding machine wherein acasing 10 surrounds a rotary grind ing stone 11 and a cooperatingstationary 100 grinding stone 12. The rotary grinding stone 11 issecured to a shaft 13 which may be driven by any suitable means as froma pulley 14. The rotary grinding stone 11 is preferably of much coarsertexture than the stationary grinding stone 12. The stones are preferablyboth made of a highly refractory fast cutting grinding material such assilicon carbide.

The opposed working faces of the two stones are conjugate, that is, theopposed working faces are parallel throughout and are not dished as hasheretofore been common in the art.

In the working face of the stationary member 12, I provide awedge-shaped groove 16 which extends from the perimeter inwardly to oneside of the axis of the 4stone and which decreases uniformly in depthfrom the perimeter to the end thereof where it merges into the workingface of the stone. In order to provide suiiicient length to this groove,I may also form it with an arcuate portion 17 which bends around theaxis of the stone and which is spaced away from the axis. The directionof rotation of the rotary grinding stone 11 is indicated in Fig. 2 by anarrow 18. It will be seen from Fig. 2 that the groove is disposed onthat side of the axis of rotation so that the direction of movement ofthe working face of the rotating stone passing in front of the grooveexerts a force giving an inward component of motion to the material inthe groove. The coal to be ground is fed into the groove from a conduit19 and passes thereto by gravity.

The texture of the stationary stone is made ne enough so as to impede aslittle as possible the iiow of material through the groove and thetexture of the rotating stone 11 is made as -coarse as possible,consistent with the degree of iineness sought, so as'to exert Ysuiciently linely divided state to pass be-4 tween the stones whereuponit is subject to Y,

the greatest degree of force on the material in the groove in itspassage inwardly of the working faces of the stones. Y

y Thus the action of the rotary stone on the material while it remainsin the` groove is a packing action or one which causes the material tobe crushed against other material and the bounding walls of the grooveduringits passage inwardly. By the time it reaches the lower end of thegroove 16 it is in a with a remarkable reduction in power required perton as compared with4 apparatus heretofore known to me, the powerrequired in the test above referred to being in the neighborhood of 2 k.w. hours per ton.

The stationary stone 12 is retained by a hollow member 22 having a ringportion 23 extending entirely around the periphery thereof. The ringportion 23 is joined to the stone by melting lead or other suitablematerial and-pouring it between the stone and the ring portion as shownat 25. The ririg portion 23 is provided with a suitable number ofprotuberances or lugs 24-around its periphery which are adapted toengage with complementary stops 26 disposed around the interior of thecasing 10 and which hold the stationary member in a predeterminedposition within the casing.' The hollow member 22 is provided with anannular partition 27 which is joined to the back of the stationarymember 12 in a fluid-tight manner. A water main is shown at 28 fromwhich a iexible branch conduit 29 leads into the interior of the hollowmember 22 for circulating water therethrough and cooling the stationarystone 12. After passing through the hollow member 22 the water isdischarged through a iexible conduit 31.

The rotary member 11 is similarly retained by av hollow member 32 joinedto the rotary member as previously described for the stationary member.The member 32 is provided with a hub-like portion 33 having openings 34therein which, in effect, act as the vanes of a pump. The shaft 13 isprovided with a passage 36 so that it is hollow and it is provided,interiorly of the hollow member 32, with a plurality of passages37.Cooling water from the main 28 'isintroduced into the end of the passage36 of the shaft 13 at 38. Thepassages 37, upon rotation of the shaft 13act. asvanes of a pump and discharge the water-.from the it is pumpedoutwardly thereof by action of the passage 34 in the hub portion 33 andis thence discharged through a discharge' conduit 39.

On the outer side of the hollow member 22 there is arranged a spring 41abutting against the casing 10 and exerting a force for holding the lugs24 0f the member`22 against the stops 26, so that the stationary memberis yieldingly held in a predetermined position with respect to therotary member. By this yielding means, the stones are relatively dis-The position of the rotary member with re-.

spect to the stationary member is adjustable by means of a thrustbearing 46 which is movable longitudinally of a holding pedestal 48 bymeans of a screw and nut connection 49 and 51.

In case there should be axial movement of the stationary member 12 suchas when iron or other hard foreign material is inadvertently fed intothe mill, it will be obvious that a considerable amount of unpulverizedmaterial might pass through the mill., In order to obviate this asmuchas possi le, I provide a gate or valve 53 in the feed conduit 19 andcontrol the closing of the gate 53 by an electromagnetic device, orsolenoid, 54. The gate 53 is normally held in .an open position by meansof a spring 56. The solenoid 54 is included in an electrical circuit 57which is controlled by a switch 58. lThe switch 58 has a sliding stem 59vbearing against the outside of the member 22 and `held thereagainst byaction of a spring 60. Upon axial movement of the stone 12 the-switch 58is closed, completing the circuit 57, energizing the solenoid 54, andeffecting a closing of the gate 53 and thus shutting oi the supply ofmaterial to be ground to the machine. As soon as the stationary stone 12has regained its normal position, the circuit 57 is again opened by thespring 60 and the spring 56 reopens the gate 53, permitting the machineto resume operation. The clearance between the switch points ispreferably made'such that the gate 53 is held closed as long as thestationary stone 12 is only slightly displaced axially with re spect tothe rotative stone 11.

Referring now to Fig. 5, I show a grinding machine embodying a pluralityof grinding units. In this machine, the casing is divided intocompartments, such as 61a and 62, each similar to the casing 10 alreadydescribed. Disposed within the compartment 61a is a rotary grindingstone 63 and a stationary grinding stone 64 similar to the grindingstones already described. Likewise, in the section 62 there is disposeda rotary grinding stone 66 and a stationary grinding stone 67. Therotary grinding stones 63 `and 66 are secured to a common shaft 68 whichmay be driven by a pulley 69. Material to be ground is admitted to thecompartment 61a'through a conduit 71 and to the compartment 62 through aconduit 72. Pulverized, material, after passin through the grindingelements is discharged through discharge conduits 73 and 74, from whenceit may be conveyed to points of use. I

The shaft 68 is provided with an interior passage 7 6 which opensthrough passages 78 and 79 to hollow retaining members 81 and 82,

both similar to the retaining member 32 Ereviously described. Theretaining mem ers Sland 82 are provided with hollow hub portions 83 and84, the hollow hub portions being provided with outlet ports 86 and 87.When the machine is running, water is admitted to the passage 76 from aconduit 89 from whence it is pumped by action of the rotating shaft, aspreviously described, into the interior of the retaining members andfrom thence outwardly by the pumping action of the hub portions thereofso as to cool the rotating stones 63 and 66. The stationary stones arecooled in the same manner as described for the single unit.

From the example shown, it will be apparent that my improved, grindingapparatus may comprise any desired number of units, all driven from acommon shaft. Thus it may be designed for any desired capacity byselecting the required number of units.

In Figs. 4 and 7, I show a modified form of a rotating grinding stonewhich may be capable of more edectively causing the fuel in the `feedgroove 16 to pass between the relatively rotating faces of the stones.In these figures the rotating stone is indicated at 91.

InV its working face there is provided a series of pockets 92. Thepockets 92 are of such radial depth that their outer boundaries areconjugate with the outer boundary of the feed groove 16 of thestationary stone. The effect of these pockets 92 passing before the feedgroove is to draw the material near the lower end of the groove andfurther inwardly of the groove and thus increase the rate of grinding ofthe unit.

Referring now to Fig. 6 of the drawing, I show a further modified formof my invention, wherein a grinding machine embodying two grinding unitsof the general character rheretofore described, are embodied within asingle casing. In this figure, a casing 101 encloses a pair ofstationary grinding elements 102 and 103. Both of these stationarygrinding elements are similar to those heretofore described and do notrequire further description. The working faces of the stationarystones102 and 103 are arranged facing toward each other, and between the twois located a two-faced rotating element 104, with its two facescooperating with the stationary stones 102 and 103. The rotating element104 is provided with a hollow retaining member 106 mounted on a shaft107. The shaft 107 has a passage 108 extending therethrough andterminating in the interior of the retaining member 106. A secondpassage 109 also extends through the shaft from the in terior of theretaining member 106 and termioperation, water under ressure is admittedfrom a conduit 114 into t e passage 108 from whence it is dischar edinto the interior of the member 106. A er passing into the interior ofthe member 106 and cooling it, it is pumped outwardly thereof by theaction of the pump 112.

The stationary grinding stones 102 and 103 are arranged to be cooled inthe same manner as previously described and need not be again.

repeated.

From the foregoing, it will be, apparent that I have devised an improvedgrinding machine which is compact, eiflcient, and which requires theminimum of power for its operation. f

While I have shown my invention in several forms, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleofvvarious other changes and modifications, without departing from thespirit thereof, and I desire, therefore, that only such limitationsshall, be placed thereupon as are imposed by the prior art or as are specically set forth in `the appended claims.

1. Ina grinding machine, a rotary grinding stone, a hollow retainingmember having a ring portion embracing and retaining the stone and ahollow hub-like portion with openings in said hub-like portion, a hollow`rotary shaft secured to the rotary member and having passages from thehollow thereof opening into the hollow of the retaining member, andmeans for introducing a cooling fluid into the hollow shaft whereby itis pumped into the hollow retaining member by rotation of the shaft andoutwardly thereof by the rotation of the hub portion of the retainingmember.

2. In a grinding machine, means for feeding materialtobeground to themachine, a

pair of coaxially' arranged relatively rotatable grinding members havingconjugate working faces, means for iixedly holding one of the membersagainst movement longitudinally of its axis, yielding means for holdingthe other member against movement longitudinally of its axis, means forshutting ofi' the supply of materiall to the machine, anelectro-magnetic `device for controlling the shutting off means, anelectric circuit for the electro-magnetic device, and means effectivematerial to be ground to the deeper portion of said groove.

n 4. In a grinding machine, a rotary grinding stone, a stationarygrinding stone cooperating with the rotary grinding stone and having itsworking face` conjugate with the working face of the rotary stone, saidstationaryA stone being rovided with a Wedge-shaped feed groove 1n itsworking face extendlng parallel to and spaced from a radius of the stoneand extending from the outer periphery inwardly and being curved in thedirection of rotation of the rotar stone as it approaches the inner areao the stationary stone, said groove being so arran ed with respect tothe rotating stone and to 1ts direction of rotation that the action ofthe rotating stone draws the material to be ground inwardly from theperiphery of the stationary stone, said vrotary stone being of coarsertexture than the stationary stone.

5. In a grinding machine, the combination of a pair ofrelatively-movable grinding elements having cooperating working faces,one of said grinding elements having an elongate feed groove in theworking face thereof, said groove extending in the general direction ofrelative movement ofthe other grinding ele- "ment and being ofdecreasing depth in said direction, the other of said grlnding elementsbeing of a coarser texture than the one grinding element, and means forfeeding the material to be ground to the deeper portion of said groove.

In testimony whereof, I have hereunto subscribed my name this nineteenthday of April,

HARRY H. BATES.

upon longitudinal'movement of the yielding means for completing theelectric circuit and closing oif'the supply of material.

3. In a grinding machine, the combination of a stationary grindingelement, a rotary grinding element of relatively coarser texture

